Allow duplicated variable names in dependency

fastapi/dependencies/utils.py

@@ -816,7 +816,7 @@ def get_body_field(*, dependant: Dependant, name: str) -> Optional[ModelField]:
     model_name = "Body_" + name
     BodyModel: Type[BaseModel] = create_model(model_name)
     for f in flat_dependant.body_params:
-        BodyModel.__fields__[f.name] = f
+        BodyModel.__fields__[f.alias] = f
     required = any(True for f in flat_dependant.body_params if f.required)
 
     BodyFieldInfo_kwargs: Dict[str, Any] = {"default": None}

tests/test_dependency_body_duplicated_variable.py

@@ -0,0 +1,126 @@
+from typing import Awaitable, Callable, List
+from unittest.mock import ANY
+
+import pytest
+from fastapi import Body, Depends, FastAPI
+from fastapi.testclient import TestClient
+
+app = FastAPI()
+
+
+def make_field(name: str) -> Callable[..., Awaitable[str]]:
+    async def inner(value: str = Body(..., alias=name)) -> str:
+        return value
+
+    return inner
+
+
+@app.post("/example")
+def example(
+    field_0: str = Body(...),
+    _field_1: str = Body(..., alias="field_1"),
+    _field_2: str = Depends(make_field("field_2")),
+    _field_3: str = Depends(make_field("field_3")),
+) -> List[str]:
+    return [field_0, _field_1, _field_2, _field_3]
+
+
+openapi_schema = {
+    "openapi": "3.0.2",
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "paths": {
+        "/example": {
+            "post": {
+                "summary": "Example",
+                "operationId": "example_example_post",
+                "requestBody": {
+                    "content": {
+                        "application/json": {
+                            "schema": {
+                                "$ref": "#/components/schemas/Body_example_example_post"
+                            }
+                        }
+                    },
+                    "required": True,
+                },
+                "responses": {
+                    "200": {
+                        "description": "Successful Response",
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "title": "Response Example Example Post",
+                                    "type": "array",
+                                    "items": {"type": "string"},
+                                }
+                            }
+                        },
+                    },
+                    "422": ANY,
+                },
+            }
+        }
+    },
+    "components": {
+        "schemas": {
+            "Body_example_example_post": {
+                "title": "Body_example_example_post",
+                "type": "object",
+                "properties": {
+                    "field_0": {"title": "Field 0", "type": "string"},
+                    "field_1": {"title": "Field 1", "type": "string"},
+                    "field_2": {"title": "Field 2", "type": "string"},
+                    "field_3": {"title": "Field 3", "type": "string"},
+                },
+                "required": ["field_0", "field_1", "field_2", "field_3"],
+            },
+            "HTTPValidationError": ANY,
+            "ValidationError": ANY,
+        }
+    },
+}
+
+
+client = TestClient(app)
+
+
+def test_openapi_schema():
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == openapi_schema
+
+
+def _field_missing(name):
+    return {
+        "loc": ["body", name],
+        "msg": "field required",
+        "type": "value_error.missing",
+    }
+
+
+@pytest.mark.parametrize(
+    "body_json,expected_status,expected_response",
+    [
+        [
+            {},
+            422,
+            {
+                "detail": [
+                    _field_missing("field_2"),
+                    _field_missing("field_3"),
+                    _field_missing("field_0"),
+                    _field_missing("field_1"),
+                ],
+            },
+        ],
+        [
+            {"field_0": "a", "field_1": "b", "field_2": "c", "field_3": "d"},
+            200,
+            ["a", "b", "c", "d"],
+        ],
+    ],
+)
+def test_endpoint(body_json, expected_status, expected_response):
+    response = client.post("/example/", json=body_json)
+    assert response.status_code == expected_status, response.text
+    assert response.json() == expected_response